This invention utilized in the medical field, generally relates to an apparatus for the humidification of inspired gases and the administration of aerosolized medication in connection with mechanical ventilators, or anesthesia devices.
Hygroscopic condensers humidifiers (HCH), heat and moisture exchangers (HME), or an artificial nose are well known in the art. These devices are routinely used for the humidification of inspired gases during mechanical ventilation.
These devices essentially work by conserving heat and moisture from the exhaled humidified gas during the exhalation phase from a patient, then recycling the heat and moisture to the subsequent inspiratory phase to humidify the dry gas from the ventilator. Recent studies have indicated, patients requiring mechanical ventilation with adequate hydration, without secretion problems, and no history of severe lung disease, can tolerate these devices for extended periods of time. Also the studies reveal, there are no increased risk of nosocomial infections with the use of these passive humidification devices, compared to heated humidification.
Due to the challenges to reduce costs in providing medical care, and as the studies have shown positive results, there is an increased acceptance and justification for the utilization of an HME.
A patient requiring mechanical ventilation with the usual method of an electronic humidification apparatus demand constant observation. For example the respiratory practitioner or nurse must assure that the reservoir of the humidifier is maintained with an adequate level of water, as well as the alarm system and heater are operating properly, and to assure a physiological proximal airway temperature.
Often the ventilator circuit must be drained from the condensation to prevent the potential drowning of a patient, and to maintain proper ventilator function. This requires often disconnecting the ventilator circuit temporarily from the patient. Another method may employ the connection of a container inline in the ventilator circuit, and a vacuum applied to remove the condensate collected in the container.
Heated wire circuits are frequently employed to reduce the amount of water condensation in the ventilator circuit. However, there is a greater cost associated with the combination of an electronic humidifier and heated wire circuit, compared to an electronic humidifier alone.
In most cases, a patient requiring mechanical ventilation will receive an aerosolized medication with a nebulizer, or metered dose inhaler (MDI). If a nebulizer is used to aerosolize a bronchodilator, the HME must be quickly removed from the ventilator circuit, and replaced with the nebulizer prefilled with a liquid medication, and xe2x80x9cTxe2x80x9d adaptor. After the nebulization is complete, the nebulizer and xe2x80x9cTxe2x80x9d adaptor are quickly disconnected, and then reattach the HME to the ventilator circuit.
If a sidestream nebulizer with xe2x80x9cTxe2x80x9d adaptor were connected in series in a position prior to the HME, obviously the aerosol would be filtered out, and the patient would not receive the aerosolized medication. Also, the added moisture from the aerosol would rapidly clog the HME. If the nebulizer and xe2x80x9cTxe2x80x9d adaptor were connected in series between the artificial airway and the HME, the patient would receive some medication, but likewise any excess aerosol would rapidly clog the HME.
The obstruction of the heat and moisture exchanging unit from the added excessive moisture will cause an increased resistance to the inspiratory gas flow, resulting in an increase work of breathing of the patient. This can have a dramatic effect on the debilitated patient, particularly during synchronous intermittent mandatory ventilation, pressure support, or spontaneous breathing with continuous positive airway pressure.
Preferably the exchange of components occurs synchronously during the brief period of time between the end of the exhalation phase, and just prior to the next inspiratory phase. The capability of the practitioner to exchange these components without interruption of ventilation, becomes increasingly more difficult with increased frequency of ventilation. If a patient is receiving continuous positive airway pressure, cessation of positive pressure occurs during the disconnection of the circuit, resulting in an intermittent drop in the intrathoracic pressure to the level of atmospheric pressure.
Obstruction of the HME device does not readily occur following a few actuations with an MDI. Therefore the HME is usually not removed prior to the use of an MDI alone. However, the HME should be removed with the combination of an MDI and spacer device, due to the added deadspace volume.
Another disadvantage of frequent disconnections of the ventilator circuit to attach a nebulizer, are the increase risk of nosocomial infections from the hospital environment, or secondary to improper hand washing technique. Moreover, the medical personnel has an increased risk of occupational hazards to the exposure of infectious airborne pathogens from a patient, such as tuberculosis, antibiotic resistant bacteria, and potential lethal viruses.
U.S. Pat. No. 5,505,568 issued to Altadonna sets forth a HUMIDITY MOISTURE EXCHANGER in which the HME having a first and second chamber, the second chamber with a pair of fluid ports. Inside the housing, is a filter or heat and moisture collecting material. To permit the uninhibited passage of aerosol from the nebulizer, the absorbent material is removed from the second chamber area, and temporarily stored within the first chamber area.
Although the device is designed to obviate the need for ventilator circuit disconnection, the device requires additional components and a nebulizer to administer an aerosol. It is unclear whether the described sealing engagement to minimize potential deadspace, could also provide an adequate seal to prevent aerosol clogging the filter, or heat and moisture collecting material when temporarily stored in the second chamber.
U.S. Pat. No. 5,546,930 issued to Wikefeldt sets forth a PATIENT CONNECTOR WITH HME, FILTER, AND NEBULIZER CONNECTION in which a Y-piece is to provide an inhalation and exhalation conduit, a patient conduit for connecting the nipple to the Y-piece, an HME disposed in the patient conduit, a nebulizer connector between the nipple and the HME, or an inhalation connector downstream to the HME for connecting the patient conduit to the nebulizer. In another embodiment a powder inhaler is also provided in connection to the nipple so that powder can be supplied to the patient.
Although Wikefeldt, has developed a method to permit the introduction of aerosols in conjunction with an HME without the interruption of mechanical ventilation, the apparatus reveals a substantial increase in the deadspace and requires several external connections of flexible tubing, and connected nebulizers. This has a disadvantage due to the increase number of connections resulting in an increased risk of potential leaks and ventilator circuit disconnection. An increase in the deadspace volume will increase the alveolar partial pressure of carbon dioxide, which could have a deleterious effect on a patient diagnosed of chronic obstructive airway disease. When an aerosolized medication is delivered by the nebulizer, a major portion of the aerosol exhaled by the patient is taken up by the HME.
While the foregoing devices are representative of the prior art, to provide an aerosolized medication in combination with an HME device, without the interruption of mechanical ventilation, which require adaptors, additional components, and nebulizers, these devices do not describe the instant invention claimed.
Several objects and advantages of the present invention are:
(a) to provide a convenient method for the safe delivery of both humidification and aerosolization of medication with mechanical ventilators or anesthesia devices;
(b) to provide a method to maintain the continuity of a closed ventilator circuit when administering an aerosolized medication, and preventing the interruption of mechanical ventilation to a patient;
(c) to provide a method to maintain the continuity of a closed ventilator circuit, to reduce the incidence of nosocomial infections resulting from frequent disconnections of the ventilator circuit, when administering an aerosolized medication;
(d) to provide a method to maintain the continuity of a closed ventilator circuit, to reduce the exposure and occupational hazards of airborne infectious bacterial and/or viruses, from a patient to medical personnel;
(e) to provide a method to conveniently add moisture such as an aerosolized isotonic saline for the hydration of the respiratory tract, thus reducing the incidence of inpissated secretions and airway occlusion;
(f) to provide a method to reduce the number of components. Therefore reducing personnel time by eliminating the requirement to exchange components, to connect a nebulizer in a ventilator circuit with a heat and moisture exchange unit.
(g) to provide a method to deliver an aerosolized medication in conjunction with a heat and moisture exchange device, with a minimum of added deadspace volume.
In accordance with the present invention there is provided a device for both humidification and aerosolization for connection to a mechanical ventilator, or anesthesia device. The apparatus comprising of a first housing containing a material capable of absorbing heat and moisture from the exhaled air and transferring the heat and moisture to the inhaled air. A second housing for a nebulizer, is rotatable with respect to the first housing to provide an aerosol.
The first housing having an output fitting to be connected to an artificial airway of a patient. The second housing having an input fitting to be connected to a ventilator circuit and a second connection to a pressurized gas supply to the nebulizer. The first housing is partitioned into chambers. A mid chamber having at the forward end and integrated with the first housing, a flexible diaphragm.
In other embodiments the mid chamber is constructed of a separate corrugated, or flexible casing. Disposed in the mid chamber, are two sections of an absorbent material, or a heat and moisture exchanger optionally impregnated with conventional hygroscopic substances. Two chambers lateral to the mid chamber provide passageways for the conveyance of the aerosol.
Internal to the the mid chamber, and between the two sections of the absorbent material, is a reciprocating member to open and close valves. The reciprocating member is pulled backward and pushed forward by a linkage with the rotatable second housing. The linkage is provided by two pins at the rearward end of the reciprocating member, which engage two arcuate channels. Each arcuate channel is offset at an incline, having an arc length of 90 degrees, and located oppositely 180 degrees with respect to the other arcuate channel. In the forward position, the valves divert the primary gas flow or inspiratory stream to bypass the lateral chambers, to pass through the absorbent material and through the output fitting to the artificial airway. At the end of the inspiratory phase, the patient passively exhales through the output fitting, into the absorbent material to conserve heat and moisture.
When the second housing is rotated 90 degrees counterclockwise, the reciprocating member is pulled backward, by the rotation of the arcuate channels which engage the two pins. In the pulled backward position, the reciprocating member positions the valves to divert the inspiratory stream to bypass the heat and moisture exchanger, and to pass through the lateral chambers, through the output fitting, to the artificial airway of the patient. At the end of the inspiratory phase, the patient passively exhales through the output fitting, through the lateral chambers and through the ventilator circuit.
The second housing provides a reservoir for receiving a liquid, a liquid nozzle, and a gas nozzle which is supplied by a pressurized gas source by means of a pressurized gas connector, an instillation port with cap to inject a liquid medication. The second housing or nebulizer, is rotatable 90 degrees clockwise or counterclockwise on a conduit extending from the first housing. Therefore the conduit also provides an axle for the second housing. The conduit having rectangular openings are normally closed by a concentric cylindrical sleeve of the second housing. The concentric sleeve having the same sized rectangular openings, are 90 degrees out of alignment with respect to the openings of an internal conduit, to provide a rotational sleeve valve. This prevents the inspiratory stream from the ventilator escaping out of the instillation port when removing of the cap to instill the liquid medication. The closed openings on the conduit prevent back pressure regurgitation of liquid from the reservoir, and the spillage of liquid into the heat and moisture exchanger and reduction of the deadspace volume when not delivering an aerosolized medication.
In the horizontal orientation of the second housing, the reservoir is filled with an appropriate quantity of liquid medication, via the instillation port. The second housing is then rotated 90 degrees counterclockwise. The vertical orientation of the second housing will allow the liquid medication to gravitate to a region of the liquid reservoir to be aspirated and aerosolized, when the pressurized gas source has been switched on to the gas nozzle. The 90 degree counterclockwise rotation opens the rectangular openings of the conduit automatically, to allow the aerosol from the interior of the second housing to be combined with the inspiratory stream. After the aerosolization is complete, the second housing is returned to the horizontal orientation by rotating the second housing 90 degrees clockwise to resume the inspiratory stream through the heat and moisture exchanger.
The horizontal to vertical orientation of the second housing or nebulizer, is readily visualized by the medical personnel. This has the advantage to determine at a glance, whether the device is adjusted for the inspiratory stream to pass through the heat and moisture exchanger, or the device is adjusted for the inspiratory stream to deliver an aerosol, during operation of the nebulizer
In another embodiment, the input fitting is equipped with a nozzle and metered dose inhaler (MDI) adaptor. In this configuration, the second housing is rotated 90 degrees counterclockwise, and the MDI is actuated in the usual manner. The reservoir of the second housing, and lateral chambers of the first housing provides a spacer device for the MDI.
In another embodiment, the mid chamber of the first housing provides a passageway for the conveyance of the aerosol, and the lateral chambers contain the heat and moisture exchange unit. Internal to the mid chamber is a reciprocating member, which is pushed forward or pulled backward by the same mechanism as described above, relative to the 90 degree clockwise and counterclockwise rotation of the second housing. The reciprocating member is comprised of a resilient material having side walls. At each end of the reciprocating member, the side walls collapse or expand to provide valves. When the second housing is in the horizontal orientation, the reciprocating member is pulled backward to provide a force to collapse the valves. This prevents the inspiratory stream from entering the mid chamber. The inspiratory stream from the ventilator by means of the internal conduit, will bypass the second housing and is directed out the openings of the mid chamber, through the heat and moisture exchange unit, to the output fitting, to the artificial airway. At the end of the inspiratory phase, the patient passively exhales through the output fitting, and through the absorbent material, to conserve heat and moisture.
The 90 degree counterclockwise rotation of the second housing in the vertical orientation pushes the reciprocating member forward. This releases the closing force on the resilient valves, and therefore the valves expand. The side walls of the reciprocating member in the forward position also closes the openings of the mid chamber. The inspiratory stream from the ventilator flowing through the second house entraining the aerosol from the interior chamber of the second housing, to bypass the heat and moisture exchange unit through the output fitting to the artificial airway. The patient passively exhales through the mid chamber through the ventilator circuit.